Personality and mood characteristics were studied in epileptic patients before and after unilateral left or right temporal lobe resection or intracarotid amytal injection. Physiologic reactions (skin conductance and EEG) were monitored during evocative procedures. The research examined the role of the left and right temporal lobes in emotional perception and expression, and how brain injury alters these functions. Right temporal lobectomy (RTL) patients showed a pattern of hypoarousal with rapid habituation whereas left temporal lobectomy (LTL) patients showed hyperarousal and increased vigilance. In a behavioral paradigm, RTL patients were more responsive to failure than LTL patients who showed dulled activation.